Automatic cut off device



March 31, 1959 s.B`.1-|BBL1NG AUTOMATIC CUT oFF DEVICE Filed Dec. so,1954 United States Patent O national Business Machines Corporation, NewYork, N.Y., a corporation of New York Application December 30, 1954,Serial No. 478,716 '7 clama. (cl. 191-17) This invention relates totypewriters and more particularly to an automaticpower cut off devicefor an electricallyoperatcd typewriter.

In a conventional embodiment, the typewriter has an electric motoroperable under switch control to drive a power driving mechanism for theindividual type bars in the typewriter. Modern machines are built sothat the motor runs so quietly as not to be detected, and accordingly,it sometimes happens that the motor is unintentionally* left on forprolonged periods.

Accordingly, it is a. first object of this invention to provide animproved automatic cut olf device for the electric motor of apoweroperated typewriter.

It is a further object of this invention to provide an improvedautomatic cut off device for power operated typewriters which isautomatically resettable to its inoperative position.'

It is a further object of this invention to provide an improvedautomatic cut oi device for a power operated typewriter which is simplein construction and efficient 1n use.

Other objects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanyingdrawings,which disclose,by way of example, the principle of the invention and thebest mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 isa perspective view of some of the component parts of a powerdriven typewriter;

Fig. 2 is a section view taken along the plane 2-2 of Fig. 1 in thedirection of the arrows;

Fig. 3 is an exploded view of the cut off device shown in Fig. 2. v

Briefly, this invention relates to an. automatic cut oil device mountedin a bracket that isV pivotally supported on the typewriter forengagement with a continuously driven power roll. A drivingwheel, anoperating cam, and a climbing wheel are coaxially mounted in the bracketfor engagement with the continuously operated power roll. If the machineis left unattended for a predetermined period, the climbing wheel willfrictionally engage the operating cam which will act to cut olf thepower to the electric motor. The climbing wheel is resettable to itsrest position upon operation of selected ones of the functioning deviceof the typewriter.

Referring to the drawings, a power roll 2 is represented as beingcontinuously rotated in the direction of the arrow under the control ofan electric motor which is not shown. The electric motor is representedas being operable under the control of an electricswitch 4 having oliand on position and shown in the o position in Fig. l. The switch 4 isconventionally operated by a link system 6 which is actuated under thecontrol of a switch arm 8 pivotally mounted on a pin 10 supported by thetypewriter frame 12. If the switch arm 8 is rotated clockwise as viewedin Fig. 1, the arm 14 of the switch v 21,879,877 Patented Mar. 31, `19594 will be moved to the dotted line position, thereby en-v ergizing theelectric motor.

The improved cut oit device is shown as comprising ra bracket 16, adriving wheel 18, a power cam 20, a climbing wheel 22, and associatedmechanisms for holding the parts in assembled relation.

The cut off device is shown pivotally .mounted byy a.

pin or shaft-28 passing through apertures 30 in bracket 16, and mountedin the typewriter frame in such a manner that the driving wheel 18 andthe climbing wheel 22 are swingable into and out of peripheralengagement with the continuously rotating power roll 2. A spring 32biases the bracket normally counterclockwise about pivot 28 to maintaincontact of both the driving wheel 18and the climbing wheel 22 with thecontinuously rotated power roll 2.

The driving wheel 18 has integrally therewith a shaft 34, looselymounted about a supporting pin 36. A threaded bushing 24 is frictionallyor force fitted on the shaft 34 for rotation therewith. The threadedbushing serves the dual function of positioning the cam 20 adjacent thedriving wheel, and acting as a screw for loosely accommodating aninternally threaded bore 37 of the climbing wheel 22. A More specically,as the climbing wheel 22 is rotated counterclockwise, in Fig. 3,relative to the threaded bushing 24, the climbing wheel will move to theright towards the driving wheel 18.

The cam element 20 is loosely mounted about the drive shaft 34 and issupported by bushings 38, 40 so that the drive shaft 34 may rotatewithin its central bore 42, while the cam 20 is held in a rest position(Fig. l). The peripheral surface of cam 20 comprises a serrated surface44 and a reduced surface 46. The latter surface is normally positionedso as to be slightly spaced peripherally from the continuously rotatingpower roll 2. However, if the `power cam 2t) is rotated slightlycounterclockwise from its position shown in Fig. 1 and Fig. 3, thesmallest radius of the serrated surface 44 will engage the power roll,thereby establishing a driving relation between the power roll and camsending the latter through a liip cycle wherein the serrated surfaceofcam 20 will run in peripheral contact with the power roll 2 until afterthe point of maximum radius of serrated surface 44 has left the powerroll, whereupon the power cam 20 will continue on its own momentum untilit has reached-its rest position.

The latter position is determined by a spring wire 49 which ispositioned for tangential engagement with a corresponding iiat surface51 on the hub of the power cam 20. The spring wire 49 holds cam 20 fromrotating while t shaft 34 rotates through its center.

It has been mentioned that the climbing wheel 22 is loosely mounted onthe threaded bushing 24, which construction provides-for the gradualmoving of the climbing wheel 22 to the right as viewed in Fig. 3, as theclimbing wheel rotates counterclockwise relative to the threaded bushing24, while the loose construction (i.e. the bore 37 being greater thanthe diameter of bushing 24) permits an axial movement of the climbingwheel 22 relative to the threaded bushing 24 when the climbing wheel 22has been disengaged from the power roll. More specifically, the climbingrelationship between climbing wheel 22 and threaded bushing 24 existsonly when a radial pressure is applied between the climbing wheel andthe threaded bushing, for example, when the -climbing wheel is inengagement with the power roll. The relative axial movement can takeplace when this radial pressure is relieved as by disengaging thedriving wheel from the power roll. In order to elect this axialdisplacement, a spring 26 is axially interpositioned between theclimbing wheel 22 and the power cam 20. With this arrangement of parts,every time the climbing wheel 22 is removed from the power roll, thespring 26 will act to move the climbing wheel to the left as viewed inFig. 3, to its rest position. In a specific embodiment the threadedbushing 24 is a spirally wound spring which provides rounded threadshaving za maximum outside diameter smaller than the minimum insidediameter of the threaded wheel 22. Accordingly, when the wheel 22 is inengagement with the power roll, the threads of the wheel and the bushingspring, respectively, are in tangential engagement, with the :axis ofthe wheel 22 lbeing eccentric with respect to the bushing spring. Uponrelease from the power roll the wheel 22 will become concentric so thatthe spring 26 will slide the wheel 22 towards the left relative to thebushing vspring as viewed in Fig. 3.

In operation, the drivingwheel 18 and the climbing wheel 22 are incontinuous peripheral engagement with the power roll 2, and, therefore,both rotate in the same direction (counterclockwise as viewed in Fig.1). The climbing wheel 22, however, has a slightly smaller dam eter thanthat of the driving wheel 18; therefore, the climbing wheel will rotateat a slightly faster rate than the driving wheel 18 and accordingly, itwill rotate relative to the threaded shaft 24 thereby permitting theclimbing wheel 22 to move to the right along the thread carried by theshaft 24. After some predetermined period, depending upon the length ofthe threaded shaft 24, and the rate of relative rotation between theshaft and climbing wheel, the right side of the latter (as viewed inFigs. l and 3), will come into frictional engagement with the hub of thepower cam 20, which frictional engagement will tend to rotate the powercam 20 in spite of the restraining force of spring 49 so that thesmallest point of serrated surface 44 will engage the power roll andthus initiate a tlip cycle.

As the power cam 20 goes through the llip cycle, the graduallyincreasing radius with respect to the central supporting shaft 36 willrock the bracket 16 clockwise about the supporting stud 28 as viewed inFig. l, a distance determined by the maximum radius of the serratedsurface 44. This clockwise pivoting of the bracket 16 acts through aconnecting link 50 on a yoke 52 carried by the link 6, and accordingly,the link 50 will act to pull the toggle arm 14 of the switch 4 from thedotted line position to the solid line position, thus shutting olf thepower to the electric motor (not shown).

In order to disable the cut olf mechanism, so that it will not shut offthe switch while the typewriter is being operated, provision is made forresetting the climbing wheel to its rest position every time certainones of the typewriter function key are operated. To illustrate thisresettingprinciple without being limited to a reset through only theillustrated function, the bracket 16 of the automatic cut off device isconnected via the arm 54 to the shift mechanism.

Reference is made to U.S. Patent '2,15 17,989 to Dodge, which describesin complete detail the case shifting mechanism for an IBM typewriter,but briefly, the depression of the shift lever S6 conditions a powermechanism (not shown) to rock a shift plate 58 about its supporting stud60. In the reference patent, connections are made from the plate 58 tothe type basket supporting means for vertically displacing the basket toposition either the upper or lower case of the type bars for printing.In the drawings, Fig. 1 shows the plate S in its rest position or lowercase position and when the plate 5S is rotated counterclockwise aboutstud 60, to move the basket to an upper case position, the pin 62 willrotate counterclockwise about the supporting stud 60 thereby pushing onarm 54 which will lift the bracket 16 away from the power roll 2. Assoon as the bracket is rocked, slightly--just far enough to relieve the.driving engagement between the power roll and the climbing wheel 22,-the spring 26 will act to displace the climbing t 1i wheel 22 axiallyback to its start position. It will be noted that arm 54 has a deep yoke63 acted on by pin 62. The purpose of this structure is that the extentof throw of arm 54 is controlled; i.e. depending on the depth of theyoke, the pin 62 will move through a considerable distance before thearm 54 moves, and consequently, the bracket 16 will be only displacedslightly from the position of Fig. l, and not far enough to shut off theswitch 4.

Operation With this mechanism, the normal operation of the automatic cutoff device is such that the climbing wheel 22 and the driving wheel 18will be in engagement with the power roll 2 to permit the smallerdiameter of the climbing wheel to produce relative movement with respectto threaded bushing 24. Accordingly, the climbing wheel will movegradually axially towards the power cam 20. When the climbing wheel hasreached a frictional engagement with the hub of power cam '20, thelatter will be rotated into engagement with the power roll therebyelfecting a flip cycle, which in turn, will cut off the switch of thetypewriter. If, at any stage'during the climbing of the wheel 22 towardsthe cam 20, the bracket 16 is rocked clockwise about its supportingshaft 28, then the spring 26 will automatically displace the climbingwheel 22 axially to its left hand position to reset it to start the cutoff period running over again.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to a preferredembodiment, it will be understoodl that various omissions andsu-bstitutions and changes in the form and details of the deviceillustrated and in its operation may be made by those skilled in the-artwithout departing from the spirit of the invention. It is the intention,therefore, to be limited only as indicated lby the scope of thefollowing claims.

What is claimed is:

l. In a power driven typewriter-having a power roll, driving meanstherefor, and an electrical switch for coutrolling said driving means,'an automatic cut olf device comprising a driving wheel, a power cam, aclimbing wheel, and bracket means mounting said parts in co-axialalignment, means pivotally mounting said bracket means for movement froma rest position wherein said wheels are in peripheral engagement withsaid power roll to an operative position, said climbing wheel-having aslightly smaller diameter than that of said driving wheel to provide fora relative rotational movement therebetween, means operable in responseto said differential movement for advancing said climbing wheellaterally toward said driving wheel from a normal or rest position to anactuating position wherein said climbing wheel is in frictional drivingengagement with said power cam to urge the latter into peripheralengagement with said power roll to initiate a cam flip cycle, meansmounting said power cam on said bracket means to move the latter to itsoperative position in response to said power cam going through a flipcycle, and means interconnecting 'said bracket means and said switch toshut off said switch when said bracket means is rocked to its operativeposition.

2. In a power driven typewriter having a power roll, driving meanstherefor, and an electrical switch for controlling said driving means,an automatic cut ot device comprising a driving wheel, a power cam, aclimbing wheel, and bracket means mounting said parts in co-axialalignment, means pivotally mounting said bracket for movement from arest position wherein said wheels are in peripheral engagement with saidpower roll to' an operative position, said climbing wheel having aslightly smaller diameter than that of said driving wheel to provide fora relative rotational movement therebetween, means operable in responseto said differenti-al movement for advancing said climbing wheellaterally' toward said driving wheel from a normal or rest position toan actuating position wherein said climbing" wheel is in frictional4driving engagement with said power cam to urge the latter intoperipheral engagement with said power roll to initiate a cam flip cycle,means mounting said power cam on said bracket means to move the latterto its operative position in response to said power cam going through aip cycle, means interconnecting said bracket means and said switch toshut off said switch when said bracket means is rocked to its operativeposition and spring means carried by said bracket means for restoringsaid climbing wheel to its rest position when said climbing wheel isrelieved from peripheral contact with said power roll.

3. In a power driven typewriter having a power roll, driving meanstherefor, and an electrical switch for controlling said driving means,an automatic cut off device comprising a driving wheel, a power cam, aclimbing wheel having a diameter slightly smaller than that of saiddriving wheel and bracket means mounting the same in sequential co-axialalignment, means pivotally mounting said bracket for movement from anormal position wherein said wheels are in peripheral engagement withsaid power roll to an operative position, spring means biasing saidbracket to its normal position, said power cam having a relieved portionnormally positioned proximate said power roll and spaced therefrom,screw thread means mounted for rotation with said driving wheel, saidclimbing wheel having a threaded bore centrally thereof loosely fittingover said screw thread means whereby when said climbing wheel and saiddriving wheel are in peripheral engagement with said power roll therelative rotation between said screw thread means and said climbingwheel causes the latter to advance laterally towards said power cam,means responsive to the movement of said climbing wheel toward saidpower cam for urging the latter into peripheral contact with said powerroll thereby initiating a flip cycle of said power cam, said power cambeing dimensioned to rotate said bracket means from its rest position toits operative position as said power cam goes through a ilip cycle, andmeans interconnecting said bracket means and said typewriter switch toshut off the latter when said bracket means is moved to its operativeposition.

4. In a power driven typewriter having a power roll, driving meanstherefor, and an electrical switch for controlling said driving means,an automatic cut off device comprising a driving wheel, a power cam, aclimbing wheel having a diameter slightly smaller than that of saiddriving wheel and bracket means mounting the same in sequential co-axialalignment, means pivotally mounting said bracket means for movement froma normal position wherein said wheels are in peripheral engagement withsaid power roll to an operative position, spring means biasing saidbracket means to its normal position, said power cam having a relievedportion normally positioned proximate said power roll and spacedtherefrom, screw thread means mounted for rotation with said drivingwheel, said climbing wheel having a threaded bore centrally thereofloosely tting over said screw thread means whereby when said climbingwheel and said driving wheel are in peripheral engagement with saidpower roll the relative rotation between said screw thread means andsaid climbing wheel causes the latter to advance laterally towards saidpower cam, means responsive to the movement of said climbing wheeltow-ard said power cam for urging the latter into peripheral contactwith said power roll thereby initiating a flip cycle of said power cam,said power cam -being dimensioned to rotate said bracket means from itsrest posi tion to its operative position as said power cam goes througha llip cycle, means interconnecting said bracket means and saidtypewriter switch to shut olf the latter when said bracket means ismoved to its operative position and spring means carried by said bracketmeans for restoring said climbing wheel to its rest position when saidclimbing wheel is relieved from peripheral contact with said power roll.

5. In a power driven typewriter having rotatable power imparting means,driving means therefor, and an electrical switch for controlling saiddriving means, an automatic cut off device comprising a bracketpivotally mounted in said typewriter for movement from a rest positionto an operative position, linkage means interconnecting said bracket andsaid switch to shut off the latter when said bracket has been moved toits operative position, and actuating means carried by said bracket forrocking the latter from its rest position to its operative positionafter a predetermined uninterrupted period, said actuating meanscomprising a pair of wheels of different diameters coaxially mounted insaid bracket for rotation in response to the operation of said rotatablepower imparting means when said bracket is in its rest position, meansfor displacing one of said wheels laterally in response to apredetermined diferential rotation of said wheels, and cam meansoperated in response to the lateral displacement of said one wheel forrocking said bracket from its rest position to its operative position.

6. In a power driven typewriter having -a power roll, a driving motorand a switch for control thereof, an automatic cut off device comprisinga pair of wheels mounted for rotation about a common axis and driven -bythe power roll at different speeds, a differential screw connectionbetween said wheels, whereby there will be relative movement of one ofthe wheels along said axis with respect to the other, and means electivewhen said relative movement exceeds a predetermined amount for causingoperation of said switch to stop said motor.

7. In a power driven typewriter having a driving motor and a switch forcontrol thereof, a pair of wheels mounted for rotation about a commonaxis, means actuated by said motor for driving said wheels at differentspeeds, and means responsive to a predetermined differential move mentbetween said wheels for causing operation of said switch to stop saidmotor.

References Cited in the le of this patent UNITED STATES PATENTS1,557,457 Hawley Oct. 13, 1925 2,602,529 Smathers July 8, 1952

